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PHASE CHANGE MATERIALS
Phase Change Material

Thermal Energy Storage
TES is a technology that stocks thermal energy by heating or cooling medium, so that the
stored energy can be used at a later time for heating and cooling applications and power
generation.
Types of thermal energy storage:
1) Sensible heat storage
2) Latent heat storage
3) Thermochemical heat storage
Latent Heat Storage: Phase change materials (PCM) are ‘‘Latent’’ heat storage materials.
PCM have been applied to increase the thermal storage capacity of different system. Heat
is absorbed or released when the material changes from solid to liquid and vice versa.
Therefore, PCM readily and predictably change their phase with certain input of energy
and release this energy at a later time.

Phase change method[1]
1) Higher thermal storage capacity compared to sensible energy storage in water. This leads to
smaller required storage. Only a true advantage if only small useful temperature difference can
be achieved.
2) Relatively constant temperature during charging and discharging
3) Burner cycle for the backup generation unit and therefore their CO and HC emission can be
reduced.

Properties of PCM[2]
1) Melting point should be in the desired temperature range.
2) High latent heat of fusion per unit volume to store more energy in a given volume.
3) High thermal conductivity to assist charging and discharging of energy.
4) Low changes in volume during phase change and low vapor pressure to avoid
containment problems.
5) Non-flammable and non-toxic.
6) Chemically stable.
7) Low cost and low containment cost.
8) Low vapor pressure (<1 bar) at the operational temperature.

Phase change material[3]

Inorganic Material[3]
1) Salt Hydrate:
It may be regarded as alloy of inorganic salt and water forming a typical crystalline solid of general formula
AB.nH2O
AB.nH2O=AB.mH2O + (n-m)H2O
Example: Water of Crystallization
CuO + H2SO4 = CuSO4 + H2O
(CuSo4.5H2o) Hydrated salt
5.H2O= Water of Crystallization
A salt hydrate usually melts to either to a salt hydrate with fewer moles of water.

Properties of Salt Hydrate:
1) High latent heat of fusion per unit volume
2) Relatively high thermal conductivity
3) Small volume changes on melting
Three types of behavior of melted salt can be identified:
1) Congruent
2) Incongruent
3) Semi congruent

2) Metallic
This category of PCM includes the low melting metals and metal
eutectics.
Properties :
1) Low heat of fusion per unit weight
2) High heat of fusion per unit volume
3) High thermal conductivity
4) Low specific heat
5) Relatively low vapor pressure

Overview about Organic Materials
Organic Materials
• possess the ability to absorb and release the large quantity of latent
heat during phase change process over a certain temperature range
• are naturally existing petroleum bi-products such as naphtha,
gasoline, fuel oil, bitumen, and hexane [3].
• have their unique phase change temperature
• generally have the temperature range between -70 C to 250 C
• undergo solid-liquid, solid-solid phase transition during heating and
cooling processes [3]

Temperature effect [18]

Classification of Organic Materials [18]
(a) Paraffin Materials (b) Non-paraffin Materials
Paraffin wax Rubi-therm Dry granules

Paraffin Materials
• It consists of a mixture of mostly straight chain n- alkanes CH3–
(CH2)–CH3.
• The crystallization of a CH3 chain release a large amount of latent
heat.
• However, under cost consideration, only technical grade paraffin may
be used in latent heat storage systems.
Paraffin Freezing range(C) Heat of Fusion (KJ/KG)[3]
6106 42 – 44 189
5838 48 – 50 189
6035 58 – 60 189
6499 66 – 68 189

• The materials have phase change temperature below 15 C are used in
cooling cycles while the materials who have above 90 C phase change
temperature are used in absorption refrigeration cycles.
• Moreover, PCMs having in between 15 C to 90 C are used in heating
cycles.
• Paraffin is safe, reliable, non corrosive, and less expensive material.
• Some undesirable properties are [3] :
(i) Low thermal conductivity
(ii) Non compatible with plastic container
(iii) Flammable
• Above three effects can be partially eliminated by modifying the wax
and the storage system.

Non-Paraffin Materials
• They are different from the paraffin materials because all the
materials have unique properties.
• They should not be exposed to excessively high temperature.
• Properties [3] :-
(i) high heat of fusion
(ii) varying level of toxicity
(iii) instability at high temperature
(iv) mild corrosive

Phase diagram of eutectic mixture[5] [6]
Ta1
L1 composition
Ta2
Ta3
Ta4
Proeutectic α
Liquid
Proeutectic α
Proeutectic α
eutectic β
eutectic α
Liquid

Cooling curve for L1 composition
Ta1
Tb1
Temperature

Phase diagram of eutectic composition[5]
Ta2

Cooling curve for eutectic composition
Ta2
Liquid mixture
α+β in solid phase
Temperature
Time

Eutectic materials[3]

Eutectic mixture of Galactitol and Mannitol[4]

Phase diagram of Galactitol and Mannitol [4]
Eutectic composition 30:70 G/M
Melting Temperature:153◦ C
Heat of fusion: 292 J.g-1

Advantages of eutectic material in latent heat
storage
• It has high latent heat of fusion at lower melting point.
• It has lowest melting temperature than the mixed material
• Its operating temperature is in the range of 25 to 180 C which is most
preferable for solar water heater, solar air heater and agriculture
heating.

Applications of PCM[7]
• Latent heat battery
• Heating in buildings
• Solar water heater
• Cold storage and sports ware

Latent heat battery[7]
• Stores the heat from radiator of car.
• The stored heat is utilized to warm up the engine during cold start.
• It can store energy for 2 days.

Heating in building[8]
• Heating:
• PCM mats are used on the roof and walls of
the building.
• It absorbs the heat during sunshine hours and
melts.
• The liquid PCM freezes during night and
releases the heat in the building.
(Source:phasechangeenergy.com) [4.2]

Solar water heater[9]
• Water is heated during sunshine hours.
• Hot water transfers heat to the PCM.
• Hot water is replaced by cold water during
night which gets heat from the liquid PCM.
Solar water heater[4.5]

• Sports ware:[10]
• PCM maintains balance between heat generated from body
and heat released to the environment.
• It reduces thermal stress.
• Cold storage:[10]
• PCM can be used in refrigerator as a backup in case of power
failure.

Advantages of PCM:[12]
• Wide melting point range from -40 C to 151 C.
• Stable for more cycles.
• Service life is high.
• High latent heat.
• Non-toxic
• Cost depends on the purity of material( From 1.5$/lb to 24$/lb)

Disadvantages:[13]
• Flammable
• Low volumetric latent storage heat capacity
• Low heat transfer rate in solid state

PCM ENCAPSULATION
BY ABULHASANSARI, MILAD

PCM Encapsulation
[14]

PCM Encapsulation Morphology
• Core ( PCM )
• Shell (Polymer or inorganic shell)
Shapes: Spherical, tubular, oval or can be made in irregular shapes
Micro Encapsulated PCM come in two different forms
Powders and Slurries. PCM with melting point from -10 to 80 C can
be microencapsulated.

Scaling Of Forces [15]

Different application of PCM
• Thermal Comfort (in building, Apparel and etc.)
• Thermal Protection
• Cooling
• Air Conditioning
• Solar Heating Systems
PCM Encapsulation

MPCM In Building [16]
PCM Encapsulation

PCM Encapsulation
• Particle size;
• Uniformity of particle size;
• Stability to mechanical stress and chemicals;
• Core-to-shell ratio, with PCM content as high as possible;

PCM Encapsulation Manufacturing [17]
Pan coating
Air-Suspension
Centrifugal Extrusion
Vibrational Nozzle
Spray Dying
Solvent Evaporation
Physical
Methods
Ionic Gelation
Coacervation
Sol-GEl
Physic-
Chemical
methods
Ionic Polymerization
Suspension
Polymerization
Emulsion
Polymerization
Chemical
Methods

Physical Methods
• Pan Coating (Shell melting temperature is lower than core)
• Air-Suspention (Volatile organic solvent; pharmaceutical, food ind.)
• Centrifugal Extrusion (No report of PCM Encapsulation but feasible)
• Vibrational Nozzel (Not used for MPCM but used for form-stable)
• Solvent Evaporation (pharmaceutical ind., dissolved or disperse)

Physical Method, Spray Drying
• Spray Drying (Low cost commercial process); Agglomerated and uncoated
Flow diagram of spray drying Schematic representation of spray drying equipment

Encapsulated Parrafin
Rubitherm RT27 with or
without CNF; average
particle size 3.9 micro
meter and encapsulation
yield of 49 %
SEM photo of prepared microcapsules

Physical Microencapsulation Comparison

Physical-Chemical Methods
• Ionic Gelation; This method is based on ability of polyelectrolytes to
crosslink in presence of multivalent counter ions Ca2+, Ba2+ and
AL3+ to form hrdrogel
• Coacervation: Simple and Complex coacervation
Simple Coacervation: Dissolved polymer with a low molecular
substance
Complex Coacervation: 12 micrometer paraffin wax mix; encapsulation
ration of 49%

• Complex Coacervation:
Flow diagram of a typical complex coacervation encapsulation process

• Ionic Gelation; This method is based on ability of polyelectrolytes to
crosslink in presence of multivalent counter ions Ca2+, Ba2+ and
AL3+ to form hrdrogel
• Sol-gel Method; polycondensation reaction of molecules
• Coacervation: Simple and Complex coacervation
Simple Coacervation: Dissolved polymer with a low molecular
substance
Complex Coacervation: Outlast and ComforTemp companies;
encapsulation ratio of 49%

Complex Coacervation

Chemical Methods
• Interfacial Polymerization: Rapid polymerization of hydrophilic and
lipophilic monomers
• Suspension Polymerization: suspension of water immiscible
reaction mixture as droplets are formed in an aqueous continuous
phase;
Vigorous agitation
Diameter various with stirring speed, volume fraction of monomer,
stabilizer concentration, viscosity of droplet, and viscosity of
suspension medium.

Chemical Methods
• Interfacial Polymerzation

Interfacial Polymerization

Chemical Methods
• Interfacial Polymerization:

Supercooling phenomenon [17]
• Supercooling is a state where liquids solidify below their normal
freezing point

Crystallization process
A. Induction phase (nuclei formation to stabilize size)
B. Crystal growth phase (nucleus absorbed)
C. Crystal regrowth phase

Supercooling
 Inorganic PCMs (such as salt hydrates) subcool more significantly
than organic PCM (such as paraffin);
 Encapsulated PCM tend to supercool severely due to the absence of
nuclei
 Supercooling increase with decrease in encapsulation size

Control Supercooling Effect
• Size of MEPCM
• Adding nucleating agent or metal additives to the PCM prior to
encapsulation
• Optimizing the composition and structure of the capsule shells

PCM Encapsulation
• Melamine-formaldehyde (MF)/n-dodecane microcapsules and gelatin/n-
tetradecane microcapsules were investigated;
 2 wt. % of 1-tetradecanol (nucleating agent) was used
 Supercooling was prevented by adding about 6 wt. % of sodium chloride
to the emulsion or 9 wt. % of 1-octadecanol in the core material. Changes
the morphology and makes Surface rough.
 Adding 20 wt.% paraffin eliminates supercooling but reduces latent heat
 5 wt. % of Rubitherm®RT58 is found to be completely prevented
supercooling of RT21 microcapsules by shifting the onset crystallization
temperature from 10.9 to 19.8 C.

PCM Encapsulation

References
[1] Gupta, E. & Reinhart, N. (n.d.). RGEES LLC innovating sustainable thermal
comfort. Retrieved from http://www.rgees.com/about.php
[2] Mishra, A., Shukla, A. & Sharma, A. (June 2015). Latent heat storage
through phase change material.
[3] Sharma, A., Tyagi, V. V., Chen, C. R., & Buddhi, D. (2009). Review on
thermal energy storage with phase change materials and
applications. Energy Renewable and Sustainable Reviews, 13(2), 318-
345. doi:10.1016/j.rser.2007.10.005
[4]Paul, A., Shi, L., & Bielawski, C. (2015). A eutectic mixture of galactitol and
mannitol as a phase change material for latent heat storage. Energy
Conversion and Management, 103, 139-146.
doi:10.1016/j.enconman.2015.06.013

[5] Imre, B. (2007).Eutectic system phase diagram. Retrieved from
https://en.wikipedia.org/wiki/Eutectic_system#/media/File:Eute
ctic_system_phase_diagram.svg
[6] Best,B.,(n.d.). Lessons for Cryonics from Metallurgy and Ceramics
Retrived from http://www.benbest.com/cryonics/lessons.html
[7] Phase change material pcm manufacturers,applications and
uses, Retrieved from
http://www.teappcm.com/applications.htm
[8] Muruganantham. K. Applications of phase change material in
building: field data vs. energy plus simulation, (2010).
[9] Kitano, H., Sagara, K., Sharma, S.D, Phase change materials for
low temperature solar thermal applications,(2004),p.31-64.

[10] Arjun, D., Hayavadana,J., Thermal energy storage materials
(PCMs) for textile applications,Volume 8,Issue 4
[11] J. Prakash, H. P. Garg, G.Datta,A solar water heater with a
built-in latent heat storage, Energy conversion and
management 25 (1985) 51-56.
[12] Phase change materials, retrieved from
http://www.puretemp.com/stories/understanding-pcms
[13] Phase change materials,retrieved from
https://en.wikipedia.org/wiki/Phase-
change_material#Organic_PCMs
[14] Tyagi, V. V., et al. "Development of phase change materials
based microencapsulated technology for buildings: a
review." Renewable and Sustainable Energy Reviews 15.2
(2011): 1373-1391.

[15] Fearing, Ronald S. "Survey of sticking effects for micro parts
handling."Intelligent Robots and Systems 95.'Human Robot
Interaction and Cooperative Robots', Proceedings. 1995 IEEE/RSJ
International Conference on. Vol. 2. IEEE, 1995.
[16] Jamekhorshid, A., S. M. Sadrameli, and M. Farid. "A review of
microencapsulation methods of phase change materials (PCMs) as a
thermal energy storage (TES) medium." Renewable and Sustainable
Energy Reviews31 (2014): 531-542.
[17] Al-Shannaq, Refat, et al. "Supercooling elimination of phase change
materials (PCMs) microcapsules." Energy 87 (2015): 654-662.
[18] Sutterlin, W. R. (2011). Introduction to thermal energy storage. The
Journal of Pharmaceutical and Biopharmaceutical Contract
Services. Retrieved from
http://www.pharmoutsourcing.com/Featured-Articles/37854-Phase-
Change-Materials-A-Brief-Comparison-of-Ice-Packs-Salts-
Paraffins-and- Vegetable-derived-Phase-Change-Materials/

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